Method and device for managing the operation of a nitrogen oxide trap, and diagnosing its ageing condition

Abstract

The invention concerns a method which consists in arranging a oxygen probe ( 21 ) of an exhaust pipe and observing that substantial unique increase of said representative signal towards a threshold value S 1 calculated from the start of the bleeding of the nitrogen oxide trap, obtained following a variation subsequent to shift of the engine from lean mixture operating conditions to rich mixture operating conditions, being used as indicator for controlling the end of the bleeding operation. The invention is characterized in that the integration of the signal representing the time between the start of the bleeding and the end of the bleeding, then the comparison of the integration value to a threshold value S 2 are used for diagnosing its ageing condition. The invention also concerns a device for implementing said method.

1. A method for managing an operation of a nitrogen oxide trap, and for diagnosing an aging condition of the nitrogen oxide trap for an internal combustion engine, comprising:
 bleeding said nitrogen oxide trap; 
 observing a change in a significant signal representative of a signal delivered by a first oxygen probe placed on an exhaust line downstream of the nitrogen oxide trap, wherein a unique substantial increase of the significant signal toward a threshold value S 1  from a start of the bleeding the nitrogen oxide trap, obtained after a variation subsequent to a transition of the engine from a lean mixture operation to a rich mixture operation, is an indicator to order an end of the bleeding; 
 determining whether the first oxygen probe operates at a high temperature or a low temperature; 
 when the first oxygen probe operates at the low temperature, integrating the significant signal over a time from the start of the bleeding to the end of the bleeding to determine an integration value, and comparing the integration value with a threshold value S 2  to diagnose the aging condition of the nitrogen oxide trap, and 
 when the first oxygen probe operates at the high temperature, measuring the time elapsed to reach the threshold S 1  from the start of the bleeding to diagnose the aging condition of the nitrogen oxide trap. 
 
   
   
     2. The method as recited in  claim 1 , wherein the first oxygen probe operates at the low temperature when the first oxygen probe operates between 400° and 500° C. 
   
   
     3. The method as recited in  claim 1 , wherein the first oxygen probe operates at the high temperature when the first oxygen probe operates between about 650° and 800° C. 
   
   
     4. The method as recited in  claim 1 , further comprising:
 utilizing, when the first oxygen probe operates at the high temperature and after the observing the change in the significant signal, a new signal comprising a new substantial increase forming a second plateau from a first plateau having a substantially constant level, obtained after the variation subsequent to the transition of the engine from the lean mixture operation to the rich mixture operation, as a supplementary indicator to order the end of the bleeding. 
 
   
   
     5. The method as recited in  claim 4 , further comprising:
 measuring a time elapsed between the first plateau and the second plateau to identify the aging condition of the nitrogen oxide trap when the first oxygen probe operates at the high temperature of between about 650° and 800° C. 
 
   
   
     6. The method as recited in  claim 1 , further comprising:
 utilizing a second oxygen probe, placed upstream of the nitrogen oxide trap, to deliver a reference signal against which a change in the signal delivered by the first oxygen probe is compared to provide said significant signal. 
 
   
   
     7. The method as recited in  claim 1 , wherein the first oxygen probe is selected from probes of the following type: an oxygen probe of an on/off type, a proportional probe, and a nitrogen oxide sensor utilizing an oxygen concentration measurement function. 
   
   
     8. The method as recited in  claim 6 , wherein the first probe and the second probe are a different type. 
   
   
     9. A device that manages an operation of a nitrogen oxide trap and that diagnoses an aging condition of the nitrogen oxide trap for an internal combustion engine, comprising:
 a first oxygen probe placed on an exhaust line downstream of the nitrogen oxide trap; 
 temperature means for determining whether the first oxygen probe operates at a high temperature or a low temperature; and 
 computation means for determining a unique substantial increase of a significant signal representative of a signal delivered by said probe from a start of bleeding the nitrogen oxide trap, the unique substantial increase of said significant signal toward a threshold value S 1  being an indicator of an end of the bleeding, and for determining the aging condition of the nitrogen oxide trap, wherein 
 when the temperature means determines that the first oxygen probe operates at the low temperature, the computation means integrates the significant signal over a time from the start of the bleeding to the end of the bleeding to determine an integration value and compares the integration value with a threshold value S 2  to diagnose the aging condition of the nitrogen oxide trap, and 
 when the temperature means determines that the first oxygen probe operates at the high temperature, the computation means measures the time elapsed to reach the threshold S 1  from the start of the bleeding to diagnose the aging condition of the nitrogen oxide trap. 
 
   
   
     10. The device as recited in  claim 9 , further comprising:
 a second oxygen probe placed upstream of the nitrogen oxide trap and configured to send a reference signal to said computation means. 
 
   
   
     11. The method as recited in  claim 6 , wherein the first probe and the second probe are an identical type. 
   
   
     12. The device as recited in  claim 9 , wherein the first oxygen probe operates at the low temperature when the first oxygen probe operates between 400° and 500° C. 
   
   
     13. The device as recited in  claim 9 , wherein the first oxygen probe operates at the high temperature when the first oxygen probe operates between about 650° and 800° C. 
   
   
     14. The device as recited in  claim 9 , wherein,
 when the first oxygen probe operates at the high temperature of between about 650° and 800° C., and after the increase of the significant signal, a new signal comprising a new substantial increase forming a second plateau from a first plateau having a substantially constant level is obtained by the computation means, 
 the new signal is obtained after a variation subsequent to a transition of the engine from a lean mixture operation to a rich mixture operation, and 
 the new signal is a supplementary indicator to order the end of the bleeding. 
 
   
   
     15. The device as recited in  claim 14 , wherein the computation means measures a time elapsed between the first plateau and the second plateau to identify the aging condition of the nitrogen oxide trap. 
   
   
     16. A device that manages an operation of a nitrogen oxide trap and that diagnoses an aging condition of the nitrogen oxide trap for an internal combustion engine, comprising:
 a first oxygen probe placed on an exhaust line downstream of the nitrogen oxide trap; 
 a computation unit configured to determine whether the first oxygen probe operates at a high temperature or a low temperature, and configured to determine a unique substantial increase of a significant signal representative of a signal delivered by said probe from a start of bleeding the nitrogen oxide trap, the unique substantial increase of said significant signal toward a threshold value S 1  being an indicator of an end of the bleeding and for determining the aging condition of the nitrogen oxide trap, wherein 
 when the computation unit determines that the first oxygen probe operates at the low temperature, the computation unit integrates the significant signal over a time from the start of the bleeding to the end of the bleeding to determine an integration value and compares the integration value with a threshold value S 2  to diagnose the aging condition of the nitrogen oxide trap, and 
 when the computation unit determines that the first oxygen probe operates at the high temperature, the computation unit measures the time elapsed to reach the threshold S 1  from the start of the bleeding to diagnose the aging condition of the nitrogen oxide trap. 
 
   
   
     17. The device as recited in  claim 16 , further comprising:
 a second oxygen probe placed upstream of the nitrogen oxide trap and configured to send a reference signal to said computation unit. 
 
   
   
     18. The device as recited in  claim 16 , wherein the first oxygen probe operates at the low temperature when the first oxygen probe operates between 400° and 500° C. 
   
   
     19. The device as recited in  claim 16 , wherein the first oxygen probe operates at the high temperature when the first oxygen probe operates between about 650° and 800° C. 
   
   
     20. The device as recited in  claim 16 , wherein,
 when the first oxygen probe operates at the high temperature of between about 650° and 800 20  C., and after the increase of the significant signal, a new signal comprising a new substantial increase forming a second plateau from a first plateau having a substantially constant level is obtained by the computation unit, 
 the new signal is obtained after a variation subsequent to a transition of the engine from a lean mixture operation to a rich mixture operation, 
 the new signal is a supplementary indicator to order the end of the bleeding, and 
 the computation unit measures a time elapsed between the first plateau and the second plateau to identify the aging condition of the nitrogen oxide trap.